This application claims the priority of German Patent Application 199 50 171.8, filed in Germany Oct. 19, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a compressed-air-operated differential lock of a motor vehicle. Preferred embodiments of the invention relate to such a differential lock which is arranged within a metallic rear-axle transmission housing having a recess, within which a piston is arranged displaceably in relation to its longitudinal axis and so as to be capable of being supported on a first claw clutch half which is arranged fixedly in terms of rotation in relation to a shaft and so as to be capable of being coupled to a corresponding second clutch half.
Such a differential lock is known from the heavy commercial vehicle Mercedes-Benz Actros. This differential lock comprises two clutch halves, by means of which a positive connection can be made in the usual way between a wheel drive halfshaft and a differential housing. The differential lock comprises a piston which is directly arranged longitudinally displaceably in a housing bore of the metal rear-axle transmission housing and which, when subjected to compressed air, can be engaged and, when relieved of compressed air, can be disengaged as a result of a spring force. For this purpose, the piston is sealed off on the circumference relative to the housing bore by means of an O-ring, and this housing bore must have a very high surface quality, in order, on the one hand, to have a corresponding sealing effect and, on the other hand, to protect the O-ring.
An object of the invention is to provide a cost-effective differential lock.
This object is achieved, according to the invention, by providing a differential lock of the above noted type wherein a plastic liner is inserted into the recess and receives the piston so as to guide the latter along said longitudinal axis.
One advantage of the invention is that the surface quality of the housing bore has to satisfy only very low requirements, so that complicated, costly and tool-wearing surface machining of the metallic transmission housing can be dispensed with.
Another advantage of the invention is that the operating reliability of the differential lock is appreciably improved, even under extreme environmental conditions with high atmospheric moisture, since moist compressed air cannot exert on the cylinder contact surface a corrosive influence which consequently increases the coefficient of friction.
A refinement of the preferred embodiments of the invention which can advantageously be mounted in a particularly simple and reliable way includes an arrangement wherein the plastic liner has an annular recess, in which is inserted a sealing ring which bears against a releasable component of the rear-axle transmission housing. Since the plastic liner and a sealing ring form a mounting unit, the possibility of xe2x80x9cforgettingxe2x80x9d to install the sealing ring or of making a positioning error under production and workshop conditions is reliably ruled out in a particularly advantageous way.
Further advantages of the invention may be gathered from the claims and from the description.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.